Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects.
Some lighting fixtures may include one or more LEDs that include more than one die. For example, some lighting fixtures may include a single LED that has multiple dies. Also, for example, some lighting fixtures may include multiple LEDs that each includes at least one die. When more than one LED die is utilized in a lighting fixture, then banding and/or color shadows may occur at the edge of the beam pattern emitted by such lighting fixtures.
For example, if a lighting fixture includes a blue, green, and red LED in combination with a reflector partially surrounding the LEDs, the LED(s) that are most closely adjacent the reflector edge will be cut-off by the reflector from the main beam of the light output. Accordingly, the main beam of the light output will have a “white” color from the combined red, green, and blue light, but color banding will be present peripherally of the main beam of the light output. The color banding may be caused, for example, by the blocking of light output from one or more LEDs by the reflector edge.
Also, for example, a lighting fixture may include multiple LED dies and light emitted by one or more of the LED dies may exit the lighting fixture uncontrolled, thereby potentially causing streaks of light to appear peripherally of the main beam emitted by the lighting fixture. These streaks of light may be present in, for example, LED-based cove lights or linear grazing fixtures mounted close to a wall or other surface. Uncontrolled light may be emitted from the sides of the fixture due to Fresnel reflections and/or mechanical restraints of the lighting fixture. Such color bands and color shadows are generally not desirable for lighting fixtures.
Thus, there is a need in the art to provide a lens that may be implemented in a lighting fixture to reduce the presence of color banding and/or color shadows present in the light output of the lighting fixture.